In the account book of the financial year 1379/80 there is proved an expenditure of “212 1/2 Marck Rostockisch” for the building of a clock and a case ("ad pixidem et ad orlogium"). A master craftsman from Lübeck ("magistro orlogii", whose name is not known, was appointed to build it. The costs comprised around 6 per cent of the city expenditures of this financial year. This means that it must have been an important purchase. More precisely: The Astronomical Clock in Rostock belongs to the earliest representative astronomical monumental clocks at the beginning of building clocks with a wheelwork.

Even though it is not written where this Clock was installed, there are many reasons that it was the ST.-MARIEN-KIRCHE:

- It was the most important among other churches in Rostock. Its main parish church with the wealthiest parish and the alderman possessed the patronage.
- On 22 November 1379 a bell for the ST.-MARIEN-KIRCHE was casted which still hangs in its tower. The coincidental cast of an (hour) bell and the construction of a clock may suggest a relation between both appointments.
- In other Hanseatic Cities the monumental clocks at that time until 1435 were or still are in the main parish churches or cathedrals.

The place of installation of this Clock in the ST.-MARIEN-KIRCHE may have been the western wall of the nave (later the organ was placed there) or the choir gallery, back to back with the main altar. It is considered as a "typical" place of Hanseatic Church Clocks at that time.

Further information about the Clock from 1379 is missing. It is supposed that the Clock was seriously damaged during the reconstruction from a hall church to a basilica in 1398. In the following half century the completion of the rebuilt building was predominant. Afterwards the responsibilities could consider a renovation and extension of the furnishings.

In 1463/70 the master craftsman Hans Düringer, who was taken from Thorn to Danzig by the city council, built a monumental clock in the MARIENKIRCHE in Danzig. In 1470 the responsibilities of Rostock, who maintained manifold political, economic and cultural relationships with Danzig, presumably appointed Hans Düringer to build a similar, even more magnificent clock in Rostock. In 1472 the construction proceeded to such an extent that Bishop Werner von Schwerin promised indulgence of 40 days to those who contributed to the completion of the new clock ("ad complendum horologium nouurn"). The building of the Clock might be completed soon after. Hans Düringer died in Danzig in 1477 und was buried there.

The Clock in Rostock is the youngest sister of the one in Danzig. Both represent a new type of clock in the Hanseatic Region. They have the same dimensions and many other similar measures. They have much in common concerning the iconographic and artistic composition. There is no other representative pair of clock that looks as similar as the ones in Danzig and Rostock. The differences of the Clock in Rostock are a result of the ambition of the responsibilities who wanted to surpass the composition of the Clock in Danzig. This is shown by the additional ring made of carved month pictures on the clock disc. There is also a second ring of zodiac (next to the clock disc) in the area of the calendar. In addtion one can find sculptures of scholars in the spandrel of the area of the calendar which might be involved to remember the previous clock.

The Clock in Rostock was more comprehensive than the one in Danzig. In 1472 the vicinity to the altar was used to build a slave clock above the altar in a westward direction. In the nave it was visible to the parish. Like it is verified in Wismar figures that were moved by the clockwork probably belonged to the slave clock. This western clock site was displaced to the inner front of the tower underneath the organ in 1621. At that time people told from an “angel and Mary“ who strike the clock every quarter of an hour. Vicke Schorler, who handed down message in his chronicle, mentioned these figures in a way that one could assume that they were well-known contemporaries. It may be supposed that the altar clock was ornamentally designed and part of the altar iconography. It has to be considered that the altar at that time was significantly lower than the one today which was built in 1720. The top level of the case might have been visible from the nave until 1720. For that reason it was ornamentally designed. For example there is a large wooden carillon from 1643 which has been inoperable since 1720.

After the Reformation with its radical changes - e. g. the renunciation from the worship of Mary and the Saints and the cult of iconography and relics - the Clocks in Danzig and Rostock were disregarded. For a long time they were considered as catholic and “pontifical” objects. There is an essential difference in the history of both Clocks: in Rostock people made an effort to restore the Clock in the first half of the 17 century involving a reconstruction closely connected with the ideas of the Reformation. At the same time the condition of Clock in Danzig more and more deteriorated. Around the middle of the 20 century this Clock was entirely lost until it finally rose like a phoenix in the last quarter of the 20 century. But this is a different story.

Around 1620 the stagnation lasting half a century seemed to be over. The time distance to the incidents of the Reformation now made it possible to think about the historic value and importance of this Clock in an unprejudiced way. The Clock was rediscovered as an urban and ecclesiastic treasure. In the first phase the altar clock on the western wall of the nave was constructed and modernized: The 24-hour-clock face was replaced by a 12-hour-clock face with a modern ring indicating a quarter of an hour, new clockworks were acquired (a clockwork, a striking mechanism indicating the hours, a striking mechanism indicating a quarter of an hour). The way to the bell in the tower became shorter.

Two decades later, in 1641/43, the time was ripe to reconstruct the Astronomical Clock as well. It obtained a strike of its own and a nickelodeon. Externally this clock was redesigned in a late Renaissance style. The ideas of the Reformation were predominant concerning the redesign of the iconography. Alltogether 949 gulden were spent for wages and material within the Thirty Years‘ War. 170 gulden were donated by notabilities of the town and church.

The "clock face" of 1643 (with the clock disc and the area of the calendar of 1472) has remained unchanged until today. The clock was exposed to danger in 1835 and during World War II.

In 1835 comprehensive works on the vaults in the church‘s choir were necessary. During this work one was not very considerate of the Clock. Hard dirt and dust caused a standstill and the bells of the music work broke. The reconstruction of the vault, the comprehensive works on the organ and the major church renovation of 1842 ate up all savings of the church parish and the clock fell behind. When the financial situation improved new damages had to be repaired at first. The standstill of the Clock lasted half a century. 1877 the duration of validity of the inscription on the calendar disc expired without renewal. In1885 willingness, money and specialists to change the situation were available. The organ builder Carl Börger und the painter H. Jenssen took overthe interior and external reconstruction of the Clock. Among all the works every single clock work was thoroughly checked up, the glockenspiel was newly casted and the white and blue paint from 1745 was removed from the case. The calendar disc was inscribed anew. The data were mainly taken from the calendar disc in Lübeck.

The MARIENKIRCHE and the Astronomical Clock survived the bombing on Rostock in April 1942 because of the preventive cautiousness, the personal dedication and the courage of the tower attendant Friedrich Bombowski und his daughter Ursula. The clock was walled in and set in concrete at the first half-year of 1943. At the end of 1951 it was laid open again. The clock survived this torture without significant damages.

In 1974 the metal restorer Wolfgang Gummelt restored the Clock’s works and its hands thoroughly. This restauration was finished in 1977. Since then all parts of the Clock have worked. Let us hope that the Clock will be maintained with the same enthusiasm in the future.